The technique for controlling wettability such as hydrophilicity or water repellency on the surface of resin is required for materials of functional resin products in various technical fields in order to control antifouling properties, flow channels of droplets, antifogging properties or the like.
Particularly many resins such as polycarbonate resins, acrylic resins, high density polyethylenes, polypropylenes, low density polyethylenes, Zeonex and polyethylenes exhibit water repellency for pure water, and therefore imparting hydrophilicity to the resin surface is important during development thereof for applications such as medical test devices, biochips, components for food applications, components for automobiles, components for agricultural applications and components for bathrooms in order to improve functionalities of the resins for the applications.
As the technique for imparting hydrophilicity to resin surface, a method has been conventionally known in which a surfactant having a hydrophilic group such as glycerine fatty acid ester monoglycerides, glycerine fatty acid esters, polyglycerine fatty acid esters, sorbitan fatty acid esters, polyoxyethylene ethylene oxide adducts and dinonylnaphthylsulphonic acid is added to the resin to enrich the resin surface with a hydrophilic group component, thereby imparting hydrophilicity. A method is also known, as disclosed in Patent Literature 1, in which electrons are allowed to collide with resin surface by corona treatment or plasma treatment to generate polar groups (OH groups and carbonyl groups) on the resin surface to impart hydrophilicity to the resin surface.
Alternatively Patent Literatures 2 to 4 disclose formation of recessions and protrusions on the surface of molded articles for utilizing the resulting pinning effect to control wettability of droplets or formation of recessions and protrusions on the surface to improve hydrophilicity.
Furthermore Patent Literature 5 discloses mixing and dispersing a water repellent resin in a base polymer and selectively dissolving the base polymer on the surface to realize superhydrophobicity.
Patent Literature 6 discloses including aramid fine particles in a fluororesin composition, soaking some of the aramid fine particles in a solvent to allow dissolution thereof to form a plurality of pores on the surface, thereby improving adhesiveness and wear resistance.
Meanwhile the technique for controlling transmittance and reflectance of light, infrared radiation or electromagnetic waves of resin molded articles has been employed in various technical fields in order to improve transmittance of optical lenses, prevent flare or decorate and color design surfaces. Conventionally, optical properties of resin molded articles have been usually controlled by forming an optical multilayer film on the surface of a resin molded article in a dry or wet manner using a vacuum deposition device or a dip coater in order to improve the optical properties.
As disclosed in Patent Literature 7, a technique for improving optical properties by utilizing recessions and protrusions has been known in which recessions and protrusions are formed on the surface of a resin molded article with an interval of at or less than a wavelength in order to, on the basis of a recession and protrusion structure, utilize the effect of interference of light, infrared radiation or electromagnetic waves, and control the transmittance or reflectance.
Patent Literature 1: Japanese Patent Application Laid-open No. 2007-160524
Patent Literature 2: Japanese Patent Application Laid-open No. H6-116430
Patent Literature 3: Japanese Patent Application Laid-open No. 2000-237678
Patent Literature 4: Japanese Patent Application Laid-open No. 2001-212966
Patent Literature 5: Japanese Patent Application Laid-open No. 2007-77201
Patent Literature 6: Japanese Patent Application Laid-open No. 2011-116821
Patent Literature 7: Japanese Patent Application Laid-open No. 2008-143162